为什么是shutil.copy2号文件比cp p慢那么多？

Question

我把一大堆文件从一个地方移到另一个地方，其中一些相当大的.wav文件，并在目的地的目录结构中改变，所以我不能批量复制目录。我最初使用的是这里推荐的copyFile函数：http://blogs.blumetech.com/blumetechs-tech-blog/2011/05/faster-python-file-copy.html

def copyFile(src, dst, buffer_size=10485760, perserveFileDate=True):
    '''
    Copies a file to a new location. Much faster performance than Apache Commons due to use of larger buffer
    @param src:    Source File
    @param dst:    Destination File (not file path)
    @param buffer_size:    Buffer size to use during copy
    @param perserveFileDate:    Preserve the original file date
    '''
    #    Check to make sure destination directory exists. If it doesn't create the directory
    dstParent, dstFileName = os.path.split(dst)
    if(not(os.path.exists(dstParent))):
        os.makedirs(dstParent)

    #    Optimize the buffer for small files
    buffer_size = min(buffer_size,os.path.getsize(src))
    if(buffer_size == 0):
        buffer_size = 1024

    if shutil._samefile(src, dst):
        raise shutil.Error("`%s` and `%s` are the same file" % (src, dst))
    for fn in [src, dst]:
        try:
            st = os.stat(fn)
        except OSError:
            # File most likely does not exist
            pass
        else:
            # XXX What about other special files? (sockets, devices...)
            if shutil.stat.S_ISFIFO(st.st_mode):
                raise shutil.SpecialFileError("`%s` is a named pipe" % fn)
    with open(src, 'rb') as fsrc:
        with open(dst, 'wb') as fdst:
            shutil.copyfileobj(fsrc, fdst, buffer_size)

    if(perserveFileDate):
        shutil.copystat(src, dst)

这还需要很长时间，所以我只是做了一个实验，我把它换成了：

^{pr2}$

我最终得到了10倍的加速！第一个版本的复制速度约为22~25kbps，而第二个版本的复制速度约为220kbps。这对我自己来说是一个不错的方法，但是我想更好地理解为什么将来我需要开发和共享这样的代码。在